Electrical thermostats including means for changing the ambient temperature setting of the thermostat at selected times are broadly known. Typically, in a heating system for instance, such thermostats are employed to set the temperature setting of the thermostat back at night and then the following morning restore it to the previous day setting as an energy saving measure. Such action is applicable in cooling systems as well and in general is taken at the time of maximum change of activity in the room in which the temperature is to be regulated.
Available thermostats responsive to the ambient temperature are usually installed in either a low voltage or a line or high voltage two wire control circuit of the heater, furnace or air conditioner as the case may be. The thermostat includes a switch that remains closed until the selected temperature is reached.
Although setpoint changing devices using conventional electrical thermostats just described are known, all, to the inventor's knowledge, require an additional electrical circuit to power the timing mechanism that determines the day and night change in temperature setting of the thermostat. The cost and need for installing an additional electric circuit for conventional setpoint changing thermostats are believed to be serious and detrimental factors that have discouraged if not depressed the replacement market for such energy saving controls. Also, since such devices are dependent upon line voltage or house current for operation they are subject to power failure requiring the timing mechanism to be reset after line voltage is restored.